Defect inspecting method and defect inspecting apparatus

ABSTRACT

A defect inspecting method and apparatus for inspecting a surface state including a defect on a wafer surface, in which a polarization state of a laser beam irradiated onto the wafer surface is connected into a specified polarization state, the converted laser beam having the specified polarization state is inserted onto the wafer surface, and a scattering light occurring from an irradiated region where the laser beam having the specified polarization state is irradiated, is separated into a first scattering light occurring due to a defect on the wafer and a second scattering light occurring due to a surface roughness on the wafer. An optical element for optical path division separates the first and second scattering lights approximately at the same time.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 13/146,428, filed Jul. 27, 2011, the contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a defect inspecting method and a defectinspecting apparatus. More particularly, the invention relates to asurface defect inspecting method and an inspecting apparatus foraccurately and fast inspecting tiny defects on a sample surface.

BACKGROUND ART

A production line for semiconductor substrates and membrane substratesinspects defects on surfaces of the semiconductor substrates andmembrane substrates in order to ensure and improve product yields.Conventional technologies are disclosed in Japanese Patent ApplicationLaid-Open Publication No. 9-304289 (patent literature 1) and JapanesePatent Application Laid-Open Publication No. 2000-162141 (patentliterature 2). In order to detect tiny defects, these technologiescondense a laser beam into several micrometers, irradiate the laser beamonto a sample surface, collect and detect scattering light from defects,and detect a defect whose size ranges from nanometers to severalmicrometers or more.

As semiconductor devices are miniaturized, the required defect detectionsensitivity increases accordingly. There have been used sensitivityimprovement techniques such as polarization detection of scatteringlight (patent literature 3). The polarization detection can selectivelysuppress scattering light (hereafter referred to as roughness scatteringlight) resulting from sample surface roughness of a laser irradiationportion and improve the detection sensitivity.

In recent years, there is an increasing need to monitor sample surfaceroughness states other than the defect detection sensitivity. The samplesurface roughness is calculated based on the roughness scattering lightintensity and is referred to as a haze signal. The haze signal ismonitored for process management (non-patent literature 1).

CITATION LIST Patent Literature

-   Patent literature 1: Japanese Patent Application Laid-Open    Publication No. 9-304289-   Patent literature 2: Japanese Patent Application Laid-Open    Publication No. 2000-162141-   Patent literature 3: U.S. Pat. No. 6,034,776

Non-Patent Literature

-   Non-patent literature 1: December 2006 Yield Management Solutions,    http://www.kla-tencor.com/company/magazine.html

SUMMARY OF INVENTION Technical Problem

Recently, the LSI wiring is drastically miniaturized. Sizes of defectsto be detected approach the detection limit of optical inspection.According to a semiconductor roadmap, mass production of 36 nm node LSIis scheduled to start in 2012. There is a need for capability ofdetecting a defect as small as a DRAM half pitch. For example, thedefect includes a scratch due to a particle or COP (Crystal OriginatedParticle) attached onto a wafer or due to polishing.

The scattering light occurs when the laser is irradiated to a defect.The relationship of I∝d̂6 is known, where I denotes the intensity of thescattering light and d denotes the particle diameter of a defect. Thatis, reducing the defect size drastically decreases the resultingscattering light. It is necessary to increase the scattering lightgenerated from a fine defect.

Applying a high laser output is a technique of increasing the generatedscattering light. However, this technique increases the temperature ofan irradiated object and may damage a sample.

As described above, the polarization detection is an effective techniqueof improving the detection sensitivity while suppressing a temperaturerise on the sample surface. However, it is difficult to concurrentlyensure the polarization detection and the haze measurement. Aninspection apparatus converts the detected scattering light into anelectric signal and separates the electric signal into frequency bands.High-frequency components are processed as a defect signal.Low-frequency components are processed as a haze signal. Suppressing theroughness scattering light due to the polarization detection greatlyreduces the haze signal and may degrade the haze measurement accuracyand stability.

As seen from the above, problems are: (1) suppressing damage on a wafer;and (2) concurrently improving the defect detection sensitivity usingthe polarization detection and measuring haze signals.

It is an object of the present invention to provide an inspection methodand an apparatus that concurrently improve the defect detectionsensitivity using the polarization detection and measure haze signalswhile suppressing damages on samples.

Solution to Problem

In order to address the above-mentioned problems, the present inventionprovides a light source, a defect optical detection system, and a hazeoptical detection system independently of each other. The light sourceirradiates a laser beam to a sample. The laser beam uses a wavelengthband that allows less energy to be absorbed. After the light sourceirradiates the laser beam, the defect optical detection system detects adefect scattering light occurring from a defect. The haze opticaldetection system detects a roughness scattering light occurring from awafer surface roughness. Polarization detection is independentlyperformed on scattering lights detected by the two optical detectionsystems. Defect determination and haze measurement are performed basedon the two different detection signals. When the less energy isabsorbed, the energy applied to the wafer is not absorbed in only thevery vicinity of the wafer surface, but penetrates into the wafer.

The illumination uses any of wavelengths 405 nm, 488 nm, and 532 nm.

A half mirror, a PBS (Polarized Beam Splitter), or a dichroic mirrorperforms amplitude separation, polarization separation, or wavelengthseparation on the scattering light occurring from an irradiated regionof the wafer. Then, the defect optical detection system and the hazeoptical detection system detect the scattering light.

The two different detection systems may use the amplitude separation forthe purpose of independent detection. In such a case, switching multiplehalf mirrors with different transmittances can adjust the amount ofscattering light detected by the defect optical detection system and thehaze optical detection system.

The two different detection systems may use the wavelength separationfor the purpose of independent detection. In such a case, the differentdetection systems are provided with a light source that oscillates twodifferent wavelengths. The defect optical detection system detects ascattering light resulting from the illumination using one wavelength.The haze optical detection system detects a scattering light resultingfrom the illumination using the other wavelength.

A single optical detection system may be provided to independentlydetect a defect signal and a haze signal by using a signal separator toseparate and detect the defect signal and the haze signal at differenttimes. The optical detection system does not need amplitude separation,polarization separation, or wavelength separation.

A transmissive polarization axis can be specified for the polarizationdetection when a user inputs a film type to be inspected and comparesthe film type with a database. The database is used for the followingpurpose. Simulation is used to previously calculate polarization statesof the defect scattering light and the roughness scattering light whilethe polarization states vary with film types. The database stores a setof data containing detection conditions for maximizing defect and hazedetection sensitivities.

Advantageous Effects of Invention

The present invention can provide a defect inspecting method andapparatus capable of not only increasing irradiation energy whilesuppressing a temperature rise on the wafer surface, but also improvingthe sensitivity based on polarization detection and ensuring the hazemeasurement at the same time. These and other objects, features andadvantages of the invention will be apparent from the following moreparticular description of preferred embodiments of the invention, asillustrated in the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram illustrating a wafer surfaceinspection apparatus according to the invention;

FIG. 2 is a schematic configuration diagram illustrating a filter;

FIG. 3 is an explanatory diagram illustrating a detection signal;

FIG. 4 exemplifies a defect map and a haze map;

FIG. 5 is a schematic configuration diagram illustrating multipleoptical detection systems in different azimuthal directions;

FIG. 6 shows an inspection flowchart for the inspection apparatus;

FIG. 7 is a schematic configuration diagram illustrating a case wheretwo wavelengths are used to illuminate the wafer surface inspectionapparatus according to the invention;

FIG. 8 illustrates relation between a penetration depth and atemperature rise;

FIG. 9 is a schematic configuration diagram illustrating time sharingdetection on the wafer surface inspection apparatus according to theinvention;

FIG. 10 is an explanatory diagram illustrating timings to turn on or offa gate circuit in a signal separator;

FIG. 11 is a schematic configuration diagram illustrating multiple pixelsensors used for the wafer surface inspection apparatus according to theinvention;

FIG. 12 is an explanatory diagram illustrating in detail an imagingsystem;

FIG. 13 is an explanatory diagram illustrating an inspection method ofilluminating the same defect more than once;

FIG. 14 is an explanatory diagram illustrating a signal processingportion that illuminates the same defect more than once;

FIG. 15 is an explanatory diagram illustrating defect detection pixelsand haze detection pixels;

FIG. 16 is an explanatory diagram illustrating an inspection methodusing a photodiode shown in FIG. 14;

FIG. 17 is an explanatory diagram illustrating a signal processingportion that uses the photodiode shown in FIG. 14; and

FIG. 18 illustrates an example user interface.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in further detailwith reference to the accompanying drawings.

First Embodiment

FIG. 1 illustrates an embodiment of the present invention. Theconfiguration in FIG. 1 includes an illuminating optical system 101, anoptical detection system 102, a wafer stage 103, a circuit, and a signalprocessing portion. The illuminating optical system 101 includes a laserlight source 2, a beam expander 3, a polarization element 4, a mirror m,and a condensing lens 6. The laser light source 2 irradiates a laserbeam 200. The beam expander 3 adjusts the laser beam diameter to aspecified size. The polarization element 4 converts the laser beam intoa specified polarization state. The laser beam reflects on thereflective mirrors m. Using the reflected laser beam, the condensinglens 6 illuminates an inspection region on the wafer 1.

The laser light source 2 uses an ultraviolet or vacuum ultraviolet laserbeam, hardly penetrating the sample inside, in order to detect a defectnear (100 nm or less deep from the surface) the surface of the wafer 1.The laser light source 2 uses a visible or infrared laser beam, easilypenetrating the sample inside, in order to detect the inside (100 nm ormore deep from the surface) of a sample.

The beam expander 3 uses an anamorphic optical system and includesmultiple prisms. The beam expander 3 varies a beam diameter in only onedirection on a plane orthogonal to the optical axis and uses thecondensing lens 6 to provide spot illumination or linear illumination onthe wafer 1. Instead of the combination of the condensing lens 6 and thebeam expander 3, a cylindrical lens may be used for linear illumination.Just the cylindrical lens enables linear illumination on a wafer withoutusing the anamorphic optical system so as to vary a beam diameter inonly one direction on the plane orthogonal to the optical axis. Thecylindrical lens is effective for simplifying the optical system becausethe beam expander 3 may be omitted.

The optical detection system 102 includes a defect optical detectionsystem 102 a and a haze optical detection system 102 b. A detection lens8 condenses scattering light that is generated from a laser irradiationportion and is applied to the wafer 1. A beam splitter 9 splits thescattering light into two optical paths. The split scattering lightpasses through condensing lenses 10 a and 10 b and filters 11 a and 11b. Photomultipliers 12 a and 12 b detect the scattering light.

The beam splitter 9 provides a half mirror or a PBS, for example. Thebeam splitter 9 performs amplitude separation or polarization separationon the scattering light that is generated from the laser irradiationportion, applied to the wafer 1, and condensed at the detection lens 8.As a result, the defect optical detection system 102 a and the hazeoptical detection system 102 b can independently detect the scatteringlight.

The filters 11 a and 11 b use a polarization plate or liquid crystal andare capable of adjusting a polarization axis to be detected. The laserbeam 200 having specific polarization characteristics may be irradiatedto the wafer. In such a case, the scattering light resulting from adefect or roughness due to the laser irradiation indicates a specificpolarization state. The polarization state varies with an illuminationcondition and a detection condition. The scattering light polarizationstate can be simulated and calculated. According to respectiveillumination and detection conditions, it is possible to findpolarization axes that easily transmit or eliminate only the defectscattering light or the roughness scattering light. That is, the filter11 a allows the polarization axis to be adjusted to easily transmit onlythe defect scattering light. The filter 11 b allows the polarizationaxis to be adjusted to easily transmit only the roughness scatteringlight. As a result, the defect optical detection system 102 a can detectthe scattering light resulting from a defect with high sensitivity. Thehaze optical detection system 102 b can detect only the roughnessscattering light with high sensitivity.

As shown in FIG. 2, the filters 11 a and 11 b are divided into segments.The segments each may have different polarization axes. FIG. 2Aexemplifies a filter 20 where the polarization axis variesone-dimensionally. FIG. 2B exemplifies a filter 21 where thepolarization axis varies two-dimensionally. The examples do not limitthe number of divided segments, the division method, or polarizationaxis directions.

The beam splitter 9 uses different transmittances. Changing thetransmittances can adjust the sensitivity of the defect opticaldetection system and the haze optical detection system. For example, thedefect optical detection system 102 a is provided with the transmittanceof 50%. The haze optical detection system 102 b is provided with thereflectance of 50%. When the defect detection sensitivity is below therequired level, the transmittance for the defect optical detectionsystem 102 a is changed to 90%. The reflectance for the haze opticaldetection system 102 b is changed to 10%. The change increases thescattering light the defect optical detection system can detect.Accordingly, the defect detection sensitivity can be improved.

The photomultipliers 12 a and 12 b are used to receive andphotoelectrically convert the scattering light. The photomultipliers 12a and 12 b may be replaced by a TV camera, a CCD camera, a photodiode, alinear sensor, a sensitive image sensor using an image intensifiercombined with these devices, or a multi-anode photomultiplier. Forexample, a two-dimensional sensor can inspect a wide region at one.

The photomultipliers 12 a and 12 b generate an electric signalcorresponding to the amount of received light. The electric signal issupplied to an analog circuit 150. The following describes a processperformed on the analog circuit 150.

Due to the laser irradiation, a signal as shown in FIG. 3 is detectedfrom the irradiated portion. Roughness scattering light N0 results froma surface roughness. During the laser irradiation, the roughnessscattering light N0 is always generated and is detected as alow-frequency surge (less than several kilohertz). Shot noise n0 occursas random fluctuation when the roughness scattering light N0 enters thephotomultiplier and is photoelectrically converted. The shot noise n0 isalso detected at the same time. On the other hand, defect scatteringlight S0 occurs in pulses from a defect only during a time when thebeam, several tens of micrometers wide, passes through a positioncorresponding to the defect. The defect scattering light S0 indicates ahigher frequency than the roughness scattering light (more than severalkilohertz). When the detection signal as shown in FIG. 3 is applied tothe analog circuit, the detection signal passes through a high-passfilter to be able to extract a defect signal and passes through alow-pass filter to be able to extract a haze signal.

Accordingly, the high-pass filter is applied to an electric signal thatoccurs based on the defect scattering light detected by thephotomultiplier 12 a. The low-pass filter is applied to an electricsignal that occurs based on the roughness scattering light detected bythe photomultiplier 12 b. The analog circuit 150 further amplifies theelectric signal and converts it from analog to digital. Based on thedetection signal, a signal processing portion 151 performs defectdetermination based on a threshold process and performs a haze processbased on level determination. A CPU 152 allows a map output portion 153to display a defect map 160 and a haze map 161 as shown in FIG. 4. Thedefect map 160 is displayed based on the defect signal received duringthe inspection and coordinates. The haze map 161 is displayed based onthe haze signal received during the inspection and coordinates. An inputportion 154 includes a user interface, enabling a user to configure arecipe.

The wafer stage 103 includes a Z stage (not shown), a rotation stage 14,and a translation stage 15. The Z stage controls a chuck and height forholding the wafer 1. The rotation stage 14 rotates the wafer. Thetranslation stage 15 moves the wafer in a radial direction. The waferstage 103 performs rotational scan and translational scan so that thelaser beam spirally irradiates the entire surface of the wafer. A stagecontrol portion 155 controls a rotation speed and a translation speed soas to be able to irradiate an intended region.

The example in FIG. 1 uses one illuminating optical system 101 and oneoptical detection system 102 for the description above. Multipleilluminating optical systems and optical detection systems may be usedin multiple elevation angles (not shown). For example, an obliqueilluminating optical system illuminates a wafer at a low elevation angleθ1. A vertical illuminating optical system illuminates a waferapproximately vertically to it. A low-angle optical detection systemdetects a defect at a low elevation angle θs against a wafer. Ahigh-angle optical detection system detects a defect at an elevationangle higher than that of the low-angle optical detection system againsta wafer.

The oblique illuminating optical system generates a larger scatteringcross-section for a foreign particle than the vertical illuminatingoptical system when illuminating the particle attached onto the wafer.Accordingly, the oblique illuminating optical system increases theamount of scattering light generated from a defect and effectivelyimproves the sensitivity. The scattering light from a defect of a sizeof several tens of nanometers strongly scatters to the side of a lowelevation angle. The scattering light from a defect of a size of 100nanometers or more strongly scatters to the side of a high elevationangle. The low elevation angle optical detection system is configured todetect tiny defects. The high elevation angle optical detection systemis configured to detect larger defects. It is possible to increase therange of detectable defect sizes.

The vertical illuminating optical system increases a scatteringcross-section when illuminating a recessed defect such as a COP or ascratch on the wafer. The vertical illuminating optical system canimprove the sensitivity of detecting recessed defects. The scatteringlight from a recessed defect strongly scatters to the side of a highelevation angle. The high elevation angle optical detection system canfurther improve the detection sensitivity.

As described above, the intensity distribution of the scattering lightoccurring from a defect or elevation angle characteristics vary withdefect types such as particle, COP, and scratch and defect sizes. Theaccuracy of classifying defects or calculating defect sizes can beimproved by combining and comparing signals in the illuminationdirections and the detection directions.

FIG. 5 is an example plan view of the embodiment shown in FIG. 1. Asshown in FIG. 5, multiple optical detection systems may be provided indifferent azimuthal directions φ. The example includes the wafer 1, theilluminating optical system 101, optical detection systems 104 a through104 f, and an illumination spot 25. The optical detection systems 104 athrough 104 f each include the defect optical detection system 102 a andthe haze optical detection system 102 b. The analog circuit 150amplifies a detection signal, removes a noise from it, and converts itfrom analog to digital. The optical detection systems 104 a through 104f add scattering light signals to each other that occurred whenapproximately the same region was illuminated. The signal processingportion 151 determines a defect and a haze based on the added signal.The CPU 152 allows the map output portion 153 to display the defect map160 and the haze map 161.

There has been described the embodiment that uses the optical detectionsystems in multiple azimuthal directions. Since the optical detectionsystems are provided at multiple azimuth angles, there is the advantageof improving the defect detection sensitivity by selecting the opticaldetection system to be used or weighting a detection signal for eachdetection. The roughness scattering light varies with azimuth anglesdepending on roughness states on the wafer surface. For example, an Siwafer having the very smooth surface tends to generate the strongroughness scattering light in an incident direction of the laser beam200, that is, in an azimuthal direction along which the opticaldetection systems 104 e and 104 f are provided. An Al-deposit waferhaving the coarse surface tends to generate the strong roughnessscattering light in a direction of advancing the laser beam 200, thatis, in an azimuthal direction along which the optical detection systems104 b and 104 c are provided. To improve the defect detectionsensitivity, a possible technique uses only the detection signaldetected in the defect optical detection system provided along theazimuth angle at which the weak roughness scattering light occurs.Another technique uses a weight equivalent to the roughness scatteringlight intensity and multiplies the weight as a gain by the detectionsignal for processing.

FIG. 5 shows the example of placing six optical detection systems indifferent azimuthal directions. The number of optical detection systemsis not limited to six. The azimuthal directions for placing the opticaldetection systems are not limited. Multiple optical detection systemsneed not be placed at approximately the same elevation angle θs. Adetector need not be placed approximately at the same azimuth angle.

FIG. 5 shows the laser irradiation from the direction parallel to thelonger direction of the illumination. The longer direction of theillumination need not approximately equal the laser irradiationdirection. The illumination may be provided from a different direction.The illumination from different directions provides the advantage ofimproving the performance of classifying defects such as scratches thatare shaped directionally. The scattering light is independent of theazimuth angle when the scattering light occurs from a COP or similardefects approximately symmetric about the azimuthal direction. Thescattering light occurs almost uniformly in all azimuthal directions. Onthe other hand, the scattering light is dependent on the azimuth anglewhen the scattering light occurs from a scratch or similar defects notsymmetric about the azimuthal direction. The azimuthal characteristicsof the scattering light from scratches also depend on the azimuth anglefor the incident illumination. It is possible to improve the accuracy ofclassifying defects or calculating sizes by actively varyingillumination directions and comparing detection-related signalsavailable in azimuthal directions.

A signal processing method adds or averages detection signals fromdetectors provided in the directions of multiple azimuth angles andelevation angles. Adding signals increases the amount of detected lightand effectively improves the detection sensitivity. Averaging signalsincreases a range of detectable sizes within the dynamic range of asensor and effectively enhances the dynamic range.

The following describes a flow of a defect detection process withreference to FIG. 6. The recipe setting configures inspection conditionssuch as an illumination direction, illumination energy, and sensorsensitivity. The recipe setting includes not only a defect detectionrecipe but also a haze measurement recipe (step 170). A wafer is mountedon the stage (step 171). The inspection starts (step 172). A defect isdetermined based on a detection signal (step 173). A defect map and ahaze map are displayed (step 174).

Second Embodiment

The following describes the second embodiment of the invention withreference to FIG. 7. Basically, an example in FIG. 7 includes theilluminating optical system 101, the optical detection system 102, thewafer stage 103, the circuit, and the signal processing portion.

The illuminating optical system 101 includes illuminating opticalsystems 101 a and 101 b. The illuminating optical system 101 a includesa light source 2 a that oscillates a laser beam with the wavelength ofλ1. The illuminating optical system 101 b includes a light source 2 bthat oscillates a laser beam with the wavelength of λ2 different fromλ1. The respective light sources oscillate laser beams 200 a and 200 b.Beam expanders 3 a and 3 b adjust diameters of the laser beams 200 a and200 b to specified sizes. Polarization elements 4 a and 4 b convert thelaser beams into specified polarization states. The laser beams arereflected on the mirror m and pass through condensing lenses 6 a and 6 bso as to be irradiated to approximately the same region on the wafer 1.

The beam splitter 9 according to the second embodiment may use awavelength separation element such as a dichroic mirror. The defectoptical detection system 102 a detects the defect scattering light thatoccurs from a defect illuminated by the laser beam 200 a with thewavelength of λ1. The haze optical detection system 102 b detects thedefect scattering light that occurs from a surface roughness illuminatedby the laser beam 200 b with the wavelength of λ2.

The following describes the advantage of using two different wavelengthsto independently detect the defect scattering light and the roughnessscattering light.

FIG. 8(a) schematically shows that the laser beam 200 is irradiated tothe wafer 1 and the wafer 1 absorbs an irradiation energy. Part of theirradiation energy (201) is reflected when the wafer 1 is illuminated.The remaining energy as transmitted light 202 penetrates into the wafer1. The penetrated energy 202 continues to penetrate into the wafer 1 andis gradually absorbed as heat by the wafer 1. The energy of thetransmitted light 202 attenuates down to (1/e)² at distance d 31 fromthe surface after the penetration. The distance is hereafter referred toas a penetration depth. The energy is absorbed only in the surface layerwhen the penetration depth is small. The energy penetrates into thewafer 1 when the penetration depth is large.

FIG. 8(b) shows relation between the depth direction and the temperatureof two materials with different penetration depths. A curve 32illustrates an example of the material with a small penetration depth.The energy is absorbed near the surface of the wafer 1. The temperaturerises greatly on the surface of the wafer 1. A curve 33 illustrates anexample of the material with a large penetration depth. The energypenetrates into the wafer 1. The temperature rises moderately on thesurface of the wafer 1. The material represented by the curve 32 moreincreases the temperature on the surface of the wafer 1 than thematerial represented by the curve 33 when approximately the same energyis applied to the materials represented by the curves 32 and 33. Thepenetration depth varies with materials and illumination wavelengths.

Increasing the irradiation energy is effective for improving the defectdetection sensitivity. The description about the penetration depth abovemakes it clear that increasing the irradiation energy requires laserirradiation using a light source whose wavelength causes a largepenetration depth in wafers.

The following describes an example of illuminating an Si wafer usingwavelengths of 355 nm and 532 nm. Illuminating the Si wafer using thewavelength of 355 nm causes a penetration depth of approximately 10 nm.Illuminating the Si wafer using the wavelength of 532 nm causes apenetration depth of approximately 2 μm. From the viewpoint of thepenetration depth, it is clear that the illumination using thewavelength of 532 nm suppresses the temperature from rising andincreases the irradiation energy.

The following describes relation between the haze measurement and thepenetration depth.

For the haze measurement, it is desirable to detect only the roughnessscattering light occurring nearly from the surface roughness. Thescattering light occurring from a COP contained in the sample may bedetected as well when the illumination uses the wavelength causing alarge penetration depth. The haze measurement accuracy or stability maydegrade.

It is desirable to use the wavelength causing a small penetration depthfor illumination and detect only the roughness scattering lightoccurring nearly from the surface roughness in order to ensure the hazemeasurement accuracy or stability.

As will be understood from the above, the illumination needs to use awavelength causing a large penetration depth in order to improve theparticle detection sensitivity. The illumination needs to use awavelength causing a small penetration depth in order to improve thehaze measurement accuracy and stability.

For example, wavelengths of 405 nm, 488 nm, and 532 nm cause largepenetration depths in Si wafers. Wavelengths of 355 nm and 266 nm causesmall penetration depths in Si wafers.

According to the example in FIG. 7, there has been described that theincident elevation angle θ1 for the illuminating optical system 101 adiffers from the incident elevation angle 82 on the wafer for theilluminating optical system 101 a. There are no limitations on the twoincident elevation angles. There are no limitations on the incidentazimuth angles of the two laser beams.

While there has been described the example using one optical detectionsystem 102, multiple optical detection systems may be used. There are nolimitations on elevation angles or azimuth angles for detection by theoptical detection systems.

Third Embodiment

The following describes the third embodiment of the invention withreference to FIG. 9. Basically, an example in FIG. 9 includes theilluminating optical system 101, an optical detection system 105, thewafer stage 103, the circuit, and the signal processing portion.

The optical detection system 105 includes the detection lens 8, acondensing lens 10 a, and a filter 11 a. A photomultiplier 12 a detectsthe scattering light.

The filter 11 a uses a polarization plate or liquid crystal and isprovided with a polarization axis capable of easily transmitting onlythe defect scattering light. As will be described later, the filter 11 asynchronizes with a signal separator 34 and is configured to be able toenable or disable the polarization axis rotation or filtering.

The signal separator 34 turns on or off a gate circuit to switch adetection signal from the photomultiplier 12 a to two paths for thedefect signal and the haze signal at specified timings. In this manner,the detection signal is separated and detected.

The following describes switch timings for the signal separator withreference to FIG. 10. FIG. 10 shows relation between movement of theillumination spot 25 irradiated on the wafer during a scan using therotation stage and gate circuit timings to turn on or off the defectsignal and the haze signal in the signal processing portion. The R axisrepresents the movement direction of the translation stage 15. The θaxis represents the rotation direction of the rotation stage 14. Theillumination spot 25 occupies a region whose area is several tens ofsquare micrometers. The region for the illumination spot 25 is too smallfor the area of the wafer whose diameter is 300 mm. There is no problemwith the explanatory diagram in FIG. 10 where the R axis and the θ axiscross each other at right angles. The rotation stage 14 rotates atlinear velocity v and requires time T: (t1−t0) to pass through a length35 of the illumination spot in a shorter direction. Based on T0 as areference, the gate circuit is switched to process the detection signalas the defect signal only during a period of Δt (<T). The gate circuitis switched to process the detection signal as the haze signal onlyduring a period of (T−Δt). The detection signal is also processed as thedefect signal only during the period of Δt and as the haze signal onlyduring the period of (T−Δt) from t1, t2, and t3, thereafter. The size ofΔt is equivalent to a time period ranging from several hundreds ofnanoseconds to several microseconds. Since the gate circuit is switchedat the above-mentioned timings, a single detection system can provideeffects of the defect optical detection system and the haze opticaldetection system without leaving a region that is not detected. Theoptical detection system is omissible, thus reducing costs anddecreasing the installation space.

The filter 11 a includes the polarization axis that easily transmitsonly the defect scattering light and therefore greatly eliminates thescattering light from the surface roughness when the haze signal isreceived. A servo motor rotates the polarization axis of the filter 11 ain synchronization with the gate circuit switchover timings while thesignal separator 34 processes the detection signal as the haze signal.The polarization state is conditioned to easily transmit only thescattering light from the surface roughness. The filtering and thepolarization detection may be omitted when the haze signal is received.

Extending the time Δt increases the defect detection signal anddecreases the haze detection signal. Shortening the time Δt decreasesthe defect detection signal and increases the haze detection signal.Adjusting the time Δt can adjust the intensity of the defect detectionsignal and the haze detection signal.

The PMT 12 a generates an electric signal corresponding to the amount ofreceived light. The signal separator 34 separates the electric signalinto the defect detection signal and the haze detection signal. Theanalog circuit 150 amplifies the detection signals, removes a noise fromthem, and converts them from analog to digital as needed. The signalprocessing portion 151 determines a defect and a haze. The CPU 152allows the map output portion 153 to display the defect map 160 and thehaze map 161.

While there has been described the example using one optical detectionsystem 105, multiple optical detection systems may be used. There are nolimitations on elevation angles or azimuth angles for detection by theoptical detection systems.

Fourth Embodiment

The following describes the fourth embodiment of the invention withreference to FIG. 11. Basically, an example in FIG. 11 includes theilluminating optical system 101, an optical detection system 106, thewafer stage 103, the circuit, and the signal processing portion. Theilluminating optical system 101 includes the laser light source 2, thebeam expander 3, the polarization element 4, the mirror m, and thecondensing lens 6. The laser light source 2 irradiates the laser beam200. The beam expander 3 adjusts the laser beam diameter to a specifiedsize. The polarization element 4 converts the laser beam into aspecified polarization state. The condensing lens 6 illuminates aninspection region on the wafer 1.

The beam expander 3 uses an anamorphic optical system and includesmultiple prisms. The beam expander 3 varies a beam diameter in only onedirection on a plane orthogonal to the optical axis and uses thecondensing lens 6 to provide spot illumination or linear illumination onthe wafer 1. Instead of the combination of the condensing lens 6 and thebeam expander 3, a cylindrical lens may be used for linear illumination.Just the cylindrical lens enables linear illumination on a wafer withoutusing the anamorphic optical system so as to vary a beam diameter inonly one direction on the plane orthogonal to the optical axis. Thecylindrical lens is effective for simplifying the optical system becausethe beam expander 3 may be omitted.

The optical detection system 106 includes an imaging optical system 40and a photodiode array 41. FIG. 12 shows in detail the optical detectionsystem 106. The optical detection system 106 includes a condensing lens42, an image intensifier 43, and imaging lenses 44 and 41. Thecondensing lens 42 condenses the light scattered from the illuminationspot 25. The image intensifier 43 amplifies the scattering light. Thescattering light passes through the imaging lens 44 and is imaged ontothe photodiode array 41. The photodiode includes pixels 61 a through 61d.

The photodiode array 41 generates an electric signal corresponding tothe amount of received light. The analog circuit 150 amplifies theelectric signal, removes a noise from it, and converts it from analog todigital. The signal processing portion 151 determines a defect and ahaze. The CPU 152 allows the map output portion 153 to display thedefect map 160 and the haze map 161. The input portion 154 allows a userto configure a recipe.

The wafer stage 103 includes a Z stage (not shown), a rotation stage 14,and a translation stage 15. The Z stage controls a chuck and height forholding the wafer 1. The rotation stage 14 rotates the wafer. Thetranslation stage 15 moves the wafer in a radial direction. The waferstage 103 performs rotational scan and translational scan so that thelaser beam spirally irradiates the entire surface of the wafer. Thestage control portion 155 controls a rotation speed and a translationspeed so as to be able to irradiate an intended region.

The stage is translated at an approximate constant speed in the radialdirection (R direction). A feeding pitch signifies a distance traveledin the radial direction after the stage rotates approximately onerevolution. The stage is rotated and translated to enable the scan sothat the illumination spot spirally moves on the entire wafer surface.The length of the illumination spot 25 in the radial directionapproximately equals the feeding pitch. In many cases, one defect isilluminated only once.

The present invention uses linear illumination. The same defect isilluminated more than once by configuring the length of the illuminationspot 25 in the radial direction to be longer than the feeding pitch. Theinspection method will be described below.

According to the explanatory diagram in FIG. 13, the length of theillumination spot 25 in the radial direction is four times longer than afeeding pitch 50. A defect 60 is illuminated four times. Multipleilluminations will be described with reference to FIG. 13. At time t1,the first illumination is performed on the defect 60 at the illuminationspot 25. The pixel 61 a detects the scattering light occurring from thedefect. At time t2, the wafer rotates approximately one revolution. Theillumination spot 25 travels the distance approximately corresponding tothe feeding pitch 50 in the radial direction. The defect 60 isre-illuminated. The pixel 61 b detects the scattering light from thedefect. At times t3 and t4, the wafer rotates approximately onerevolution to illuminate the defect 60. The pixels 61 c and 61 d detectthe scattering light from the defect. As a result, the defect 60 can beilluminated four times according to the method shown in FIG. 13. Theanalog circuit or the signal processing portion adds or averages thedetected scattering lights. The illumination is not limited to fourtimes and may be performed any number of times. Increasing the number ofadditions can amplify the scattering light signal from a defect andimprove the detection sensitivity.

The photodiode 41 is not limited to include four pixels.

The following describes an addition process method in the signalprocessing portion with reference to FIG. 14. The present inventionassumes that each of the pixels detects approximately the same regionand shifts one by one each time the wafer rotates one revolution.Accordingly, the memory for storing the detection signal is shifted eachtime the wafer rotates one revolution. The memory 65 stores a signal forthe pixel 61 a at the first rotation. Thereafter, the memory 65 stores asignal for the pixel 61 b at the second rotation. The memory 65 stores asignal for the pixel 61 c at the third rotation. The memory 65 stores asignal for the pixel 61 d at the fourth rotation. This makes it possibleto add signals from approximately the same region.

While there has been described the example using one optical detectionsystem 106, multiple optical detection systems may be used. There are nolimitations on elevation angles or azimuth angles for detection by theoptical detection systems.

The image intensifier 43 is used in order to amplify and detect a weakscattering light. Instead of the image intensifier, for example, it isalso preferable to use an EM-CCD, a multi-anode photomultiplier, or anequivalent sensor that indicates a high amplification factor itself.These devices are effective for miniaturization of the apparatus becausethe optical detection system can be provided in a small space.

The photodiode array 41 is used to receive and photoelectrically convertthe scattering light. The photodiode array 41 may be replaced by a TVcamera, a CCD camera, a photodiode, a linear sensor, a sensitive imagesensor using an image intensifier combined with these devices, or amulti-anode photomultiplier.

Fifth Embodiment

A modification of the fourth embodiment will be described with referenceto FIG. 15.

The embodiment varies polarization state of the scattering light thatcan be detected for each pixel of the photodiode 41. In addition, theembodiment varies the method of switching the storage memory to be addedin the signal processing portion. FIG. 15 shows an example of thephotodiode array 41 including four pixels 61 a through 61 d. Filters 74a and 74 b are polarization plates having polarization axes that easilytransmit only the defect scattering light. Filters 75 a and 75 b arepolarization plates having polarization axes that easily transmit onlythe roughness scattering light.

The detector is provided at an azimuth angle for detection approximatelyperpendicular to the illumination direction and uses the followingexamples of polarization axes that easily transmit only the defectscattering light and the roughness scattering light. A polarization axisperpendicular to the wafer provides a polarization detection angle thateasily transmits the defect scattering light. An angle of approximately45 degrees from the direction perpendicular to the wafer provides apolarization detection angle that easily transmits the roughnessscattering light.

Attaching a filter 74 a to a photosensitive surface of the pixel 61 aconfigures a defect detection pixel 70 a. The filter 74 a includes thepolarization axis that easily transmits only the defect scatteringlight. Accordingly, the defect detection pixel 70 a detects only thedefect scattering light. Similarly, a defect detection pixel 70 bincludes the pixel 61 b and a filter 74 b and highly sensitively detectsonly the defect scattering light.

Attaching a filter 75 a to a photosensitive surface of the pixel 61 bconfigures a haze detection pixel 71 a. The filter 75 a includes thepolarization axis that easily transmits only the roughness scatteringlight. Accordingly, the haze detection pixel 70 a detects only theroughness scattering light. Similarly, a haze detection pixel 71 bincludes the pixel 61 b and a filter 75 b and highly sensitively detectsonly the roughness scattering light.

As shown in FIG. 15, a photodiode array 72 alternately includes thedefect detection pixels and haze detection pixels.

The following describes a scan method using the photodiode 72 withreference to FIG. 16. As shown in FIG. 16, the length of theillumination spot 14 in the radial direction is four times longer thanthe feeding pitch 50. The defect 60 is illuminated four times. At timet1, the first illumination is performed on the defect 60 at theillumination spot 25. The scattering light occurs from a defect or asurface roughness and is condensed at the defect detection pixel 70 a.The defect detection pixel 70 a is provided with a filter that easilytransmits only the defect scattering light. Accordingly, the defectdetection pixel 70 a eliminates the roughness scattering light anddetects a defect signal.

At time t2, the wafer approximately rotates one revolution. The secondillumination is performed on the defect 60 at the illumination spot 25.The scattering light occurs from a defect or a surface roughness and iscondensed at the haze detection pixel 71 a. The haze detection pixel 71a is provided with a filter that easily transmits only the roughnessscattering light. Accordingly, the haze detection pixel 71 a eliminatesthe defect scattering light and detects a haze signal.

At time t3, the wafer approximately rotates one revolution. The thirdillumination is performed on the defect 60 at the illumination spot 25.The scattering light occurs from a defect or a surface roughness and iscondensed at the defect detection pixel 70 b. The defect detection pixel70 b is provided with a filter that easily transmits only the defectscattering light. Accordingly, the defect detection pixel 70 beliminates the roughness scattering light and detects a defect signal.

At time t4, the wafer approximately rotates one revolution. The fourthillumination is performed on the defect 60 at the illumination spot 25.The scattering light occurs from a defect or a surface roughness and iscondensed at the haze detection pixel 71 b. The haze detection pixel 71a is provided with a filter that easily transmits only the roughnessscattering light. Accordingly, the haze detection pixel 71 a eliminatesthe defect scattering light and detects a haze signal.

The photodiode 72 may be used when the same foreign particle isilluminated several times and multiple detected signals are added. Insuch a case, the defect scattering light and the roughness scatteringlight are alternately detected each time the wafer rotates onerevolution. That is, it is also necessary to change the method ofswitching the memory that stores a detection signal corresponding to onerevolution.

The following describes an addition process method in the signalprocessing portion 151 with reference to FIG. 17. The signal processingportion 151 includes defect signal storage memory 76 and haze signalstorage memory 77.

The defect signal storage memory 76 stores a signal detected by thedefect detection pixel 70 a at the first revolution. The haze signalstorage memory 77 stores a signal detected by the haze detection pixel71 a at the second revolution. The defect signal storage memory 76stores a signal detected by the defect detection pixel 70 b at the thirdrevolution. The haze signal storage memory 77 stores a signal detectedby the haze detection pixel 71 b at the fourth revolution.

As described above, the photodiode array 72 uses two types of pixels,the defect detection pixels 70 a and 70 b and the haze detection pixels71 a and 71 b. The defect signal storage memory 76 and the haze signalstorage memory 77 are provided and store the detection signals. As aresult, it is possible to not only improve the defect detectionsensitivity based on the polarization detection, but also ensure thehaze measurement at the same time.

The embodiment provides the example of the sensor having four pixels ofwhich two defect detection pixels and two haze detection pixels are laidout alternately. There are no limitations on the number of photodiodes,a ratio of the defect detection pixels and the haze detection pixels, orthe order of placing these pixels.

For example, there may be an example of providing three defect detectionpixels and one haze detection pixel. The example can increase the numberof defect signal detections up to three. The example provides an effectof improving the defect detection sensitivity.

According to the above-mentioned example, the filters 74 a and 74 b areprovided with the polarization axis that easily transmits the defectscattering light. One of the filters may not be configured to mosteasily transmit the defect scattering light. However, the dynamic rangefor the sensor is limited. A sensor output may be saturated if the largescattering light occurs from a large foreign particle when thesensitivity is increased to detect a tiny defect. The defect size iscalculated based on the amount of detected light. The accuracy of defectsize calculation degrades if a sensor output is saturated. To solve thisproblem, the polarization axis of the filter provided for the defectdetection pixel is shifted from the polarization axis that most easilytransmits the defect scattering light. The scattering light occurringfrom a large foreign particle can be detected without saturating thesensor output. There is provided an effect of increasing the dynamicrange.

FIG. 18 exemplifies a user interface for the input portion 154. The userinterface includes sub-windows 180, 181, and 182. The sub-window 180specifies the type of a wafer to be inspected. The sub-windows 181 and182 display rates of extracting or separating defect signals and hazesignals on the detectors.

According to the invention, the optical detection system may be providedin multiple elevation angle directions and azimuth angle directions.Polarization states of the scattering light from a defect and that froma surface roughness vary with an elevation angle or an azimuth angle tobe detected. The two scattering lights polarize in oscillationdirections perpendicular to each other under some conditions. The twoscattering lights polarize in approximately the same oscillationdirection under other conditions.

Let us consider the detection system uses a detection condition thatallows the defect scattering light and the surface roughness scatteringlight to have their polarization axes perpendicular to each other. Inthis case, the detection system can detect the defect scattering lightand the surface roughness scattering light each with a purity ofapproximately 100% without attenuating them. Let us consider thedetection system uses a detection condition that allows the defectscattering light and the surface roughness scattering light to haveapproximately the same polarization axis. In principle, the detectionsystem can hardly separate the defect scattering light and the surfaceroughness scattering light from each other.

According to the above description, the azimuth angle and the elevationangle for detection almost uniquely determine the percentage ofpossibility of separating the defect scattering light and the roughnessscattering light from each other. The polarization detection conditionat that time can be almost uniquely determined. A simulation may beperformed to previously calculate polarization states of the defectscattering light and the roughness scattering light corresponding toeach detection azimuth angle and elevation angle for detection. Adatabase may be used to store detection conditions for maximizing therate of separation between the defect scattering light and the roughnessscattering light. This makes it possible to easily generate a recipe andshorten the time to generate it.

The polarization state of the scattering light from a surface roughnessvaries with the material or surface roughness of a wafer to beinspected. A database may be used to store detection conditions formaximizing the rate of separation between the defect scattering lightand the roughness scattering light in accordance with film types orsurface roughnesses. This makes it possible to easily generate a recipeand shorten the time to generate it.

There may be a detection condition that makes the polarizationseparation difficult. Even in such a case, the signal processing portionmay filter signals based on frequency bands and separately detect ahigh-frequency component as the defect detection signal and alow-frequency component as the haze detection signal.

The sub-window 180 enables selection of the film type to be inspected.For example, available film types include Si, Poly-Si, Cu, Al, W, andSiO₂ and are selectable from a pull-down menu. The operation specifiesan initial value for the polarization detection condition of eachdetector. The initial value is reflected on display contents of thesub-windows 181 and 182.

As seen from the sub-windows 181 and 182 in FIG. 18, detector A canseparate the defect scattering light and the roughness scattering lightfrom each other at approximately 100% without attenuation due to thepolarization detection. Detector B separates the defect scattering lightand the roughness scattering light from each other at approximately 80%with approximately 20% attenuation due to the polarization detection.

The selection on the sub-window 180 specifies an initial value of theseparation rate for the sub-windows 181 and 182. In addition, a user mayspecify the initial value. For example, the user may specify theseparation rate of 80% for the defect scattering light on the sub-window181 or the separation rate of 50% for the defect scattering light on thesub-window 182. In principle, however, the maximum separable rate ispredetermined for each detection condition and is displayed as a dottedline in the sub-window. The separation rate cannot be specified over themaximum value.

The separation rate may be directly entered or may be selected from apull-down menu.

According to the embodiment of the invention as described above, thepolarization detection improves the defect detection sensitivity. Inaddition, the scattering light can be detected from a surface roughnesswithout attenuation. The defect inspection and the haze measurement canbe ensured at the same time. The invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. The present embodiment is therefore to beconsidered in all respect as illustrative and not restrictive, the scopeof the invention being indicated by the appended claims rather than bythe foregoing description and all changes which come within the meaningand range of equivalency of the claims are therefore intended to beembraced therein.

The use of a laser beam with the wavelength band causing a largepenetration depth can increase the irradiation energy and improve thedetection sensitivity without damage to the wafer.

According to the embodiment of the invention, the photodiode arrayhaving multiple pixels is used to separate pixels into defect detectionpixels and haze detection pixels. It is possible to improve thedetection sensitivity based on the polarization and enable the hazemeasurement at the same time.

REFERENCE SIGNS LIST

-   -   1—Wafer    -   2, 2 a, 2 b—Laser light source    -   3, 3 a, 3 b—Beam expander    -   4, 4 a, 4 b—Polarization element    -   m—Mirror    -   6, 6 a, 6 b, 10 a, 10 b—Condensing lens    -   8—Detection lens    -   9—Beam splitter    -   11 a, 11 b, 74 a, 74 b, 75 a, 75 b—Filter    -   12 a, 12 b—Photomultiplier    -   20, 21—Polarization filter    -   25—Illumination spot    -   31—Penetration depth    -   32—Characteristics of the material having a small penetration        depth    -   33—Characteristics of the material having a large penetration        depth    -   34—Signal separator    -   35—Length of an illumination spot in the rotation direction    -   36—Timing to turn on or off the gate circuit of the defect        signal detector    -   37—Timing to turn on or off the gate circuit of the haze signal        detector    -   40—Imaging optical system    -   41, 72—Photodiode array    -   42—Condensing lens    -   43—Image intensifier    -   44—Imaging lens    -   50—Feeding pitch    -   60—Defect    -   61 a . . . 61 d—Pixels of the photodiode array    -   65—Memory    -   70 a, 70 b—Defect detection pixel    -   71 a, 71 b—Haze detection pixel    -   76—Memory for storing defect detection signals    -   77—Memory for storing haze detection signals    -   101, 101 a, 101 b—Illuminating optical system    -   102, 104 a . . . 104 f, 105—Optical detection system    -   102 a—Defect optical detection system    -   102 b—Haze optical detection system    -   103—Wafer stage    -   150—Analog circuit    -   151—Signal processing portion    -   152—CPU    -   153—Map output portion    -   154—Input portion    -   155—Stage control portion    -   160—Defect map    -   161—Haze map    -   170 . . . 174—Inspection flow    -   180 . . . 182—Sub-window    -   200, 200 a, 200 b—Laser beam    -   201—Normally reflected light    -   202—Transmitted light

1.-16. (canceled)
 17. A defect inspecting method of inspecting a surfacestate including a defect on a wafer surface, the method comprises thesteps of: adjusting a transmissive polarization axis of a polarizationfilter; irradiating a laser beam onto the wafer surface; and detecting ascattering light occurring from an irradiated region on the wafersurface via the adjusted polarization filter.
 18. The defect inspectingmethod according to claim 17, wherein the polarization filter isconfigured to enable or disable a transmissive polarization axisrotation or filtering.
 19. The defect inspecting method according toclaim 17, wherein a polarization axis of the polarization filter isadjusted to a first transmissive polarization axis for defectmeasurement or a second transmissive polarization axis for hazemeasurement.
 20. The defect inspecting method according to claim 17,wherein the method further comprises the steps of: separating a detectedsignal of the detected scattering light into a defect signal and a hazesignal.
 21. The defect inspecting method according to claim 17, whereinthe polarization filter comprises segments each of which has anindividual transmissive polarization axis.
 22. The defect inspectingmethod according to claim 21, wherein the transmissive polarization axisvaries one-dimensionally or two-dimensionally.
 23. The defect inspectingmethod according to claim 17, wherein the detected scattering light isseparated by a divider including one of amplitude division, wavelengthdivision, and polarization division.
 24. The defect inspecting methodaccording to claim 17, wherein the laser beam is irradiated from aplurality of light sources having different wavelengths.
 25. The defectinspecting method according to claim 17, wherein the laser beam isirradiated approximately vertically onto the wafer surface.
 26. Thedefect inspecting method according to claim 17, wherein the laser beamis irradiated obliquely onto the wafer surface.
 27. A defect inspectingapparatus for inspecting a surface state including a defect on a wafersurface, the apparatus comprising: an irradiator which irradiates alaser beam onto the wafer surface; a transmissive polarization filter;an adjustor which adjusts a polarization axis of said transmissivepolarization filter; and a detector which detects a scattering lightoccurring from an irradiated region on the wafer surface via thetransmissive polarization filter.
 28. The defect inspecting apparatusaccording to claim 27, wherein the transmissive polarization filter isconfigured to enable or disable a transmissive polarization axisrotation or filtering.
 29. The defect inspecting apparatus according toclaim 27, wherein a transmissive polarization axis of the transmissivepolarization filter is adjusted to a first transmissive polarizationaxis for defect measurement or a second transmissive polarization axisfor haze measurement.
 30. The defect inspecting apparatus according toclaim 28, wherein a transmissive polarization axis of the transmissivepolarization filter is adjusted to a first transmissive polarizationaxis for defect measurement or a second transmissive polarization axisfor haze measurement.
 31. The defect inspecting apparatus according toclaim 28, further comprising: a separator which separates a detectedsignal the detected scattering light into a defect signal and a hazesignal.
 32. The defect inspecting apparatus according to claim 28,wherein the transmissive polarization filter comprises segments each ofwhich has an individual polarization axis.
 33. The defect inspectingapparatus according to claim 32, wherein said transmissive polarizationfilter varies one-dimensionally or two-dimensionally.
 34. The defectinspecting apparatus according to claim 28, further comprising aseparator which separates the scattering light by a divider includingone of amplitude division, wavelength division, and polarizationdivision.
 35. The defect inspecting apparatus according to claim 28,wherein the laser beam is irradiated from a plurality of light sourceshaving different wavelengths.
 36. The defect inspecting apparatusaccording to claim 27, wherein the laser beam is irradiatedapproximately vertically onto the wafer surface.
 37. The defectinspecting apparatus according to claim 27, wherein a laser beam isirradiated obliquely onto the wafer surface.